JPS60250235A - Method and apparatus for inspecting thread surface - Google Patents

Abstract

PURPOSE:To detect the presence or degree of quality deficiency such as chattering on the thread surface at a high accuracy by irradiating the thread surface with one belt-like luminous flux to detect the reflection pattern. CONSTITUTION:A screw cut section 10A of a steel pipe 10 having the section made by cutting is irradiated with at least one belt-like luminous flux expanding in the direction of the thread axis A by a surface light source 20 and a filter 22 with a slit from the direction almost at the right angle to the thread axis A and the reflection pattern at the thread cut section 10A is taken with a TV camera 24 arranged to have the direction of the horizontal scan line coinciding with the thread axis A to obtain an image signal. Then, the image signal is processed to detect changes or the level thereof caused in a self-correlation image signal during the rotation centered on the thread axis A thereby inspecting quality deficiency of the thread surface.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thread surface inspection method and an inspection device, and in particular, to automatic quality inspection of threaded parts of steel pipes manufactured for use in oil wells, etc. 91 suitable for use,
Concerning improvements in screw surface inspection methods and inspection devices.

For use in oil drilling, etc. The 14-piece manufactured in 1993 usually has screws machined on both longitudinal ends of its casing.
In use, generally, a pipe with 2-M4 threads formed on the outer peripheral surface of the pipe at both ends and a threaded part of the pipe with the same tenth diameter are connected with a joint called a coupling, in which fine threads are machined on the inner peripheral surface of both ends. Either they are connected and used A, or each end has a threaded part with a male thread cut on the outer circumferential surface of the pipe and a threaded part with a self-thread cut cut on the inner circumferential surface of the pipe. It is used by directly screwing the connection over the cover.

In this way, steel pipes for oil wells are used for practical use by continuously connecting pipes and suspending them deep underground, but in this case, large tensile forces act on the pipes. In particular, even more severe stress will be concentrated on the threaded connection.

Therefore, a defect in the threaded connection part of a steel pipe used for such severe applications has the risk of causing a major accident, and sufficient quality inspection is required during thread cutting.

For this reason, conventionally, in the thread cutting process of U4 pipe, after thread cutting, various thread element gauges were used to inspect various thread elements such as effective thread size, taper, lead, thread height, and thread shape. Generally, screw element inspection is carried out using human visual inspection, and visual inspection is carried out to inspect minute quality defects such as chatter on the thread cutting surface, which cannot be discovered by screw element inspection, by human visual inspection. However, human visual inspection has a problem in that it may not be possible to discover minute quality defects on the thread cutting surface.

In addition, in recent years, thread element inspection, which conventionally relied on manual labor, has become possible to automatically inspect various thread elements by directly contacting the thread with a sensor probe and measuring the thread shape in three dimensions. , automation in this field is progressing rapidly. However, compared to the progress in automation in the field of measuring thread elements, no suitable testing method or testing device has been developed or put into practical use in the field of quality inspection of finished threaded surfaces. However, the automation of this process has been significantly delayed, and the process still has to rely on visual inspection by highly skilled people.

In order to solve these problems, some of the inventors have already proposed in Japanese Patent Application No. 58-167901 that the machined surface has a tI゛ which is larger than the periodic interval of the cutting unevenness. A spot-shaped light beam is irradiated, and the brightness and darkness of the spatial brightness of the scattered light that is inversely IJ = 1 from the cutting surface is detected. We have proposed a method for inspecting the properties of machined surfaces, which is characterized by detecting the presence or extent of quality defects such as chatter from spatial changes in strength.

According to this method of inspecting the properties of machined surfaces, it is possible to reliably detect the presence or extent of quality defects such as chatter on the cutting surface, and it has the excellent effect of being able to be automated. -4 However, it is possible to accurately detect and detect the presence or extent of quality defects such as chatter from the presence or absence of striped shading patterns or spatial changes in shading intensity caused by scattered light.
It wasn't always easy.

The present invention has been made in order to solve the above-mentioned conventional problems, and provides a method for inspecting a screw surface that can detect the presence or extent of quality defects such as chatter with high precision on the screw surface and can be automated. The primary purpose is to provide 4-.

In addition to the first object, a second object of the present invention is to provide a screw surface inspection device that can quickly perform an inspection with a small memory capacity.

The present invention provides a method for inspecting a thread surface, in which:
irradiating at least one band-shaped light beam that spreads in the direction of the screw axis, and scanning a periodic reflection pattern generated and covering the illuminated portion of the screw surface in the direction of the screw axis to obtain an image signal thereof; An autocorrelation calculation is performed on the image signal to form an autocorrelation image signal, and a change or amount of change that occurs in the autocorrelation image signal during rotation of the screw around the screw axis is detected to detect the change on the screw surface. The first object is achieved by detecting the presence or extent of quality defects such as chatter.

The present invention also provides a screw surface inspection device including: an illumination means for projecting a plurality of parallel belt-shaped light beams onto the screw surface, extending in the screw axial direction; Positive image means scans the lattice-like anti-Q] pattern that occurs in the screw axis direction to obtain its 1ilnfri day, and performs an autocorrelation operation on the image signal to obtain an autocorrelation image (,
413, a screw co-rotator for rotating the screw about the screw axis; and detection means for detecting a change or amount of change that occurs in the autocorrelation image signal during rotation of the screw; and from the detection result by the detection means,
Detects the presence or extent of quality defects such as chatter on the screw surface.
In this way, the second objective was achieved.

A detailed description of the present invention follows.

In general, it is known that thread chatter is caused by vibrations of the machine tool itself, the cutting machine, or the workpiece during the cutting process. In other words, the cause of chatter is the relative motion between the machine tool body (one cutting hole) and the workpiece, but the chatter is caused by self-excited vibration between the machine tool body and the workpiece system. Therefore, once the -th mark begins to occur, it is impossible to make one tot. In this way, the workpiece,
For example, in a W4 pipe for an oil well, periodic cutting unevenness occurs along the thread in the thread cutting direction, and the period changes depending on the relative frequency and cutting speed between the machine tool body and the workpiece. In addition, the size of the cutting unevenness is also different from the machine tool body and the
The relative vibration of the T material (varies depending on the size of the thread width).Furthermore, in addition to chatter, there are other factors that affect the crystal quality of the thread cutting finish, which are determined from the geometrical shape of the cutting preview and the feed rate. There are also roughness curves formed on the finished surface due to the geometric shape of the finished surface and the subtle roughness and defects of the edge of the cutting tool.

Therefore, in the present invention, the principle as shown in FIGS. 1 to 3 is used when detecting the presence or extent of quality defects on the cutting surface of a thread such as a maze. That is,
For example, a surface light source 20 and a filter with slits 22 are combined as shown in FIG. From those whose light sources themselves have the function of generating band-shaped rays,
At least one band-shaped light beam spreading in the horizontal direction (in the figure) is irradiated from a direction substantially perpendicular to the screw axis A, and the irregular pattern in the thread cutting section 10A is detected by scanning the horizontal scanning line in the direction of the screw @. The TV camera 24, which is arranged so that the direction of the A force is on, captures the image and captures the signal. At this time, the television camera 24 may move in the horizontal scanning direction, but its vertical position remains unchanged with respect to the thread cutting section 10A.

When the number of band-shaped light beams determined by the number of slits in the slit filter 22 is one, the reflection pattern imitated by this television camera 24 is determined by the pitch of the thread in the direction toward the screw axis. The result is a striped reflection pattern whose brightness changes periodically. In addition, when the number of band-shaped light beams is plural, the pitch of the threads is in the direction toward the screw axis, and the screw axis A
The result is a lattice-like reflection pattern in which the brightness and darkness change in a direction perpendicular to (vertical direction in FIG. 1) at a period determined by the interval between the band-shaped light beams. However, in the present invention, the number of band-shaped light beams is 1
It doesn't matter if it's a book or multiple books.1. Therefore, hereinafter, the case where the number of band-shaped light beams is plural will be explained as an example.

8- Next, in this state, when the thread cutting part 10A is rotated in the direction of arrow B around the thread axis A, the reflection pattern becomes
It moves in the direction of the screw shaft according to the pitch of the screw +h, and also moves and deforms in the vertical direction due to the chatter of the thread surface. Therefore, for example, Fig. 2 (when chatter component C is included)
The image signal of the reflection pattern being moved and deformed, as shown in FIG.

Here, Ryochen's autocorrelation processing is performed by removing the influence of movement changes according to the pitch of the thread from among the changes in the reflection pattern that occur during the rotation of the screw. This is to extract only changes in the reflection pattern due to periodic quality defects such as chatter.

As an image correlation means for forming an autocorrelation image signal by performing self-correlation of the @ image signal, for example, an optical system using a conventionally known ultrasonic light modulator and a Fourier modulation optical system is used. My father used a device that performs a correlation calculation and displays only the horizontal autocorrelation image of the input image in the center of the screen of the display device.
The one-dimensional autocorrelation function of the image output signal for each horizontal scan is detected by an optical correlator attached to the ultrasonic light modulator as disclosed in No. 36, and the one-dimensional autocorrelation function of the image output signal is detected on both sides of the display and displayed. can be used.

Note that the type of image correlation means is not limited to these, and the method does not particularly matter as long as image autocorrelation is possible.

An example of an autocorrelation image created by this autocorrelation process is shown in Figure 3 (corresponding to Figure 2), and the characteristics of this autocorrelation image are that the horizontal scanning line direction of the screen is The movement does not appear in the correlation output image (b) The autocorrelation output image of the input image that falls within the field of view of the television camera 24 is
Centered on the center of the display screen! [Sometimes it appears in a symmetrical stone shape. 3. Due to these features, the self-contained image of the foul pattern is always displayed in the center of the display screen without the horizontal movement of the grid pattern due to the pitch of the screw threads.

Here, if the screw has no defects such as chatter,
Even if the screw 10 is rotated, the band-shaped light beam is distorted under certain conditions, and the correlated image becomes a static lattice pattern. This correlation image of a non-defective product is hereinafter referred to as a reference pattern. On the other hand, h
If there is chatter on the same surface, a small autocorrelation pattern of chatter appears in the reference pattern as shown by the symbols in Fig. 3, and this correlation pattern is changed by the rotation of the screw.
4. Repeating random curved shapes and flashing light and dark. However, this autocorrelation pattern does not move laterally, similar to the base t pattern.

As shown in FIG. 3, since the reference pattern and the chatter correlation pattern appear within the same range on the display screen, M? It is possible to memorize the range of both sides of the display where the pattern clearly appears in a frame memory, etc., and compare Y4IIl\ at the same location for each frame, and check for chatter based on the amount of change in A. .

-] 1- The correlation pattern is unchanged in the lateral direction and is a periodic pattern determined by the pitch of the screw. In addition, when multiple strip-shaped light beams are used, a grid-like pattern is created that is repeated in the vertical direction at an interval of 6 strip-shaped light beams, so that each lattice in each lattice of a two-dimensional lattice constituted by the period of these repetitions is constant. It is also possible to measure each other and conduct a chatter test.

In this case, it is not necessary to store the entire screen in the frame memory, and it is possible to reduce the amount of memory and speed up the inspection at the same time.

Furthermore, if the screw moves up and down within the field of view of the television camera, the correlated image will also change up and down, making it difficult to set the bright spot detection location. Since the relative lit position between the point position and the chatter correlation pattern is almost the same, it is 1! If there are 6 traces (of the bright spots of the quasi-pattern),
Using this as Ml, chatter can be detected.

The present invention has been made based on the following principles.

Hereinafter, with reference to the drawings, an embodiment of an IC steel 12 gastric tube end screw inspection T1 device to which the present invention is adopted will be described in detail.

In this embodiment, as shown in FIGS. 4 and 5, the surface of the threaded portion 10A of the steel pipe 10 is illuminated with a plurality of parallel band-shaped light beams extending in the direction of the thread -11. A surface light source 20 and a filter with slits 22, a television camera 24 that scans in the direction of the screw axis a grid-like irregular pattern generated on the illuminated portion of the screw surface to obtain an image thereof, and an inspection At the same time, the steel pipe 10 is centered around the screw shaft.
A turning roller 30 for rotating at a predetermined rotational speed and a camera controller 32 for controlling the television camera 24 are used to perform an autocorrelation image of the image No. 11'' to generate an autocorrelation image signal. and an image signal processing device 34 for detecting a change or amount of change occurring in the autocorrelation image signal during rotation of the screw.

In the figure, 36 and 38 are the thread cutting part 10A,
The lower dark box and the G side dark box 40 for preventing external light from entering the surface light source 20, the slit filter 22, and the television camera 24 are the Iiii+G side dark box 38 &gIlff1Q outside (\ 42 is an entrance table roller for inserting and covering the threaded part 10A at the tip of the steel pipe 10 into the dark box during inspection. , 44Δ, 44F3, 46A, and 46B are two dark blue position detection sensors for transmitting and receiving light Qll in V) that detect the tip position of the steel pipe 10 in the front station dark box and control the input side table roller 42. It is.

The image processing device 34, as shown in detail in FIG.
-A television image analog correlation station 34A and the television image analog correlation device 34A as disclosed in US Pat.
A display device 34'B converts the image signal output from the TV image signal into an image, and a display device 34'B converts the image signal output from the TV image analog correlation device 34△ into an image. No. 3, a data calculation device 34G for distinguishing the correlation value due to chatter from the M quasi-pattern, and a display alarm device 34r for displaying and covering the first correlation due to chatter almost simultaneously with screw inspection, and outputting good news. )
It is composed of and.

As shown in detail in FIG. 4, the to-side dark box lifting device 40 is fixed to the side surface of the +-side dark box 38, and the to-end engages with a gear in the gear box 40A. It is composed of a screw 40B, a gear A7 box 40C for rotating the screw 140B, and a daytime motor 40D for rotating the gear A4 in the gear box 40C. . Therefore, u
Depending on the size of the outer diameter of AAl2O, the dark box 38 on the G side is moved downwards to reduce the intruding light as much as possible, and also to connect the measured part of the thread cutting part 10Δ surface H, the surface light source 20, the slit filter 22, and The distance from the television camera 24 can be adjusted.

The action will be explained below.

The w4 pipe 10, which is the object to be inspected in the sushi inspection device, is carried to the entry side table roller 42-hi of the thread inspection device by a flow side conveyance device (not shown), (omitted) and is sent into a dark box. Inside the dark box are position detection sensors 44A, 44B and 46A that detect the tip of the steel pipe 10.
, 46B are arranged, and first, the position detection sensor 44
The entry side table roller 42 is controlled to decelerate due to the detection of the tip by the A and 44B, and furthermore, the entry side table roller 42 is controlled to be stopped by the tip detected by the (l''/4 detection sensors 46A and 46B. Then, tA
When the steel pipe 10 is stopped so that the tip end of the pipe 10 is at a predetermined position, the turning roller 30 is raised to a height where the lower surface of the steel pipe 10 does not come into contact with the entrance table roller 42, and Turning roller 30 rotates to rotate 10 at a predetermined rotational speed. In addition, outside the M4 tube 10 (according to ¥), the - side dark box raising device 40 raises and lowers the dark box 38 on the side, and the positions of the surface light 11! 20, filter with slit 22, and television camera 24 are also adjusted. The image processing device 34 automatically inspects the screw surface.

After the surface inspection of the thread cutting part 10A is performed and the pass/fail judgment of the thread surface is carried out once, the steel pipe 10 is carried out to the outside of the dark box by the reverse rotation of the retable roller 42, and is carried out to the outside of the dark box. By a carry-out Rib (not shown), the paper is carried out to a conveyance line downstream from the input table roller 42.

Examples of the ii[ii# signal obtained in this embodiment are shown in FIGS. 7 to 10. FIGS. 7 and 8 are continuous image photographs of the results of autocorrelation processing of image signals of 18 threaded parts free of quality defects such as chatter, which are displayed on the display device 34F3, and show a light and dark pattern in a grid pattern. is the seventh
It is clear that there is no change between the figure and FIG. On the other hand, FIGS. 9 and 10 are continuous image photographs of the results of autocorrelation processing of the image *tgq of the threaded part of a steel pipe where chatter has occurred on the thread cutting surface, and are displayed on the display device 3411. Interval [Therefore, although the basic lattice pattern that is occurring has not changed, the correlation value due to chatter is superimposed on the basic pattern, and it can be seen that the correlation pattern due to chatter is changing due to the rotation of the screw. it is obvious.

In this embodiment, the surface light source 20, the slit filter 22, and the television camera 24 are fixed, and the steel pipe 10 is rotated to perform the screw inspection. Therefore, the signal line etc. can be fixed, and the configuration is simple. Note that the configuration of the thread inspection device according to the present invention is not limited to this, and the steel pipe 10 is fixed, and the surface light source 20 integrated with the phase η, the slit toy 1 filter 22, and the television camera 24 are rotated around the steel pipe 10. Alternatively, the steel pipe 10, the surface light source 20, and the filter with slits 22 are fixedly oriented,
It is also possible to perform a screw inspection by moving only the television camera 24.

In the above embodiments, the present invention was applied to inspecting the properties of the threaded end of the fA, such as chatter, but the scope of application of the present invention is not limited to this, and is applicable to other members. It can be similarly applied to screw inspection. In addition, for inspection of other objects other than screw inspection, b.
It is clear that if a certain defect exists in 114, the presence or absence of that defect can be detected.

As explained above, according to the present invention, the presence or extent of quality defects such as chatter on the surface of a screw can be detected with high precision, and automation is also possible.

[Brief Description of the Drawings] Fig. 1 is a perspective view for explaining the principle of the thread surface inspection method according to the present invention, and Fig. 2 shows an example of an image signal that is InI and includes chatter. Similarly, FIG. 3 shows an example of the autocorrelation processed image signal corresponding to FIG. 2. Fig. 5 is a sectional view taken along line v-v in Fig. 4, and Fig. 6 is a sectional view of the image processing device used in the above embodiment. Block diagrams showing the configuration, Figures 7 and 8, show the results of autocorrelation processing of image signals of threaded parts of steel pipes that are free of quality defects such as chatter. And FIG. 10 shows that chatter occurs on the threaded surface.
I took revenge on myself at the H1 station and showed the result '1 continuous picture ti
w Pf is 1, 19-10...! 14 Jin, 10△... Thread cutting part, 20... Surface light source, 22... Filter with slit, A... Threaded shaft, 24... Television camera, 30... Turn roller, 32... Camera controller, 34... Image signal processing equipment. 34A...TV image analog correlation device, 34tl.
...display device, 340...data performance device, 34 r)...display alarm device. Agent Takaya Ron (1 idiot) -20- Fig. 1 Fig. 7 Fig. 6 Fig. 9 Fig. 10 Fig. 1982 Patent Application No. 106234 2 Title of Invention Method and Inspection Device for Thread Surface 3 , Relationship to the case of the person making the amendment Patent applicant name (125) Kawasaki Steel Corporation (and 1 other person) 4. Agent 160 Address Gin Building 6, Nishi-Shinjuku-chome-12-11 Yama, Shinjuku-ku, Tokyo , a column for a detailed explanation of the invention in the specification to be amended, a column for a brief explanation of the drawings in the specification, and the drawings. 7. Contents of the amendment (1) From page 18, line 6 to line 20 of the specification [This example makes it clear... According to this example, as a result of performing autocorrelation processing on an image signal of a threaded portion of a steel pipe without quality defects such as chatter, it was confirmed that the light and dark pattern of the lattice pattern did not change. On the other hand, as a result of autocorrelation processing of the image signal of the threaded part of a steel pipe where chatter has occurred on the thread cutting surface, the basic lattice pattern that is occurring does not change depending on the thread pitch interval, but the correlation value due to chatter It was confirmed that the correlation pattern due to chatter was superimposed on the basic pattern and changed as the screw rotated. ”. (2) "Block diagram, . . . is a continuous image photograph" in lines 14 to 20 of page 20 of the specification is an r block diagram. ”. (3) Delete drawings 7 to 10. Guangkyu

Claims (2)

[Claims] (1) The screw surface is irradiated with at least one band-shaped light beam that spreads in the screw axial direction, and the periodic reflection pattern generated on the illuminated part of the screw surface is scanned in the screw axial direction. Obtaining an image signal, performing an autocorrelation calculation on the image signal to form an autocorrelation image signal, and detecting a change or amount of change that occurs in the autocorrelation image signal during rotation of the screw about the screw shaft. A method for inspecting a screw surface, the method comprising: detecting the presence or extent of quality defects such as chatter on the screw surface. (2) An illumination means that irradiates the screw surface with a plurality of mutually parallel belt-shaped light beams that spread in the screw axial direction; an image carrier means for scanning the image signal to obtain an image No. 1-1c; a double image correlation means for performing an autocorrelation calculation on the image signal to form an autocorrelation image signal; and a means for rotating the screw about the screw axis. A screw rotating means, and a detecting means for detecting a change or amount of change that occurs in the autocorrelation image signal during rotation of the screw, and detects the presence or absence of quality defects such as chatter on the screw surface from the detection result by the detecting means. 4. A screw surface inspection device, characterized in that it is configured to detect or detect the degree of the screw surface.